


I Can't Control It

by littlestephen



Category: Katekyou Hitman Reborn!
Genre: 27R, Bottom!Reborn, Explicit Sexual Content, Fluff and Smut, M/M, TOP!TSUNA, Teen Reborn, adult tsuna
Language: English
Status: Completed
Published: 2019-03-22
Updated: 2019-03-22
Packaged: 2019-11-28 02:37:07
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,384
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18202373
Author URL: https://archiveofourown.org/users/littlestephen/pseuds/littlestephen
Summary: At his birthday party, Reborn starts acting strange.Suddenly he can't control what he says or do, telling to his ex-student some... weird things.But Tsuna want some explanations.





	I Can't Control It

**Author's Note:**

> I did this... like, right now.   
> I needed to write this before this idea went away. And I always wanted some seme!Tsuna, so I did this!  
> Hope you guys like it.

            Reborn disliked birthdays.

            Actually, dislike is a meaningless and weak word to describe the feeling that the hitman had towards this fatidic day. Reborn despises and hates this day with all his strength. There was nothing good on this day. People showed up to celebrate — or, as Reborn used to say, eat the food you bought —, with small boxes called gifts and sing a shameful song. Since the hitman was born, he hated those days. Always keeping this information to himself and no one else. And if someone managed to get this information from someone, he’d gently bit them to death — Kyoya style.

            Nevertheless, there he was, the young teen, celebrating inside the Vongola Headquarters his and Decimo’s birthday — since the hitman and the brunet celebrated almost at the same day. There were a lot of allies, willing to give the tenth boss of the powerful Vongola Famiglia nice words to fill the brunet’s ego. Well, he knew the useless Sawada Tsunayoshi didn’t feel nothing but gratefulness and shyness seeing all those people congratulating him.

            If the brunet could, he would have declined the enormous party — simply choosing to have a family party with his guardians, his mother and father and some of his friends. However, Sawada Iemitsu had to open his mouth to talk shit.

            “Ah, Tsuna! You should really accept this party! Since it’s not only for you, but for Reborn too! That brat never had a party before, he’d love it!” The blond said with a grin in his reddish lips, pointing secretly towards the dark-haired teen. Iemitsu, somehow had discovered his little secret. How? Reborn would have to find out later. The hitman was about to kick the man, but, when Tsuna said those kind words, he gave up.

            “Really, Reborn?” Decimo said with widened hazel-colored eyes peering over the teen. “Then I’ll accept the party. You deserve it.”

            After the representative battle — where Tsunayoshi worked hard to find a solution to the Arcobaleno’s curse — the little baby with black suit and a fedora hat was finally able to grow. The hitman still hated that he’d have to wait for almost twenty years to get the body that he wanted to — the tall and handsome man that he was before the curse. However, for his surprise, after the sixth year growing normally, as any child, the ex-Arcobaleno started to grow two more years in only one year. Everyone was confused that in one year the little boy were six and in the next he was eight. But they started to get used to this new way of growing.

            And on that day, the hitman was officially sixteen years old. He had to admit, his body grew nicely and fast. He was almost tall enough to surpass his useless ex-student — he was still a few centimeters away. And he bragged about the muscle mass that had suddenly showed up in his abdomen and biceps. The dark-haired teen was starting to develop his old looks, and he was glad about this.

            “Reborn,” the assassin peered up, meeting those hazel-colored eyes of his ex-student, shining with amusement. “Let’s blow the candles of our cakes!” The hitman punched the young man in the belly, smirking as he heard a hard gasp coming out from the back of the man’s throat.

            “You’re showing your useless emotions, Dame-Tsuna!” The hitman pushed his fedora up, only to show his murderous gaze towards the young man. However, the brunet only laughed, curving back up, watching the teen with those kind eyes. Reborn felt something at the base of his stomach. The tenth boss put his arms around the teen’s neck, pulling the dark-haired boy closer to his body. The hitman would punch him again, but the warmth of the young man’s body was comfortable and enjoyable. ‘What are you doing? Just punch him already!’ He told himself.

            “Let’s go, Reborn, they’re waiting for us.” The brunet said, with a wide grin in his reddish lips. The hitman did nothing but stare; stare at the young man’s eyes and simply froze. Hypnotized by the man’s kind expression and warm arms, the assassin followed the brunet.  

* * *

            People were singing the ‘Happy Birthday’ song, with so much enthusiasm and happiness in their silly voices, that Reborn had to clench his fist to not sigh or roll his eyes at the wondrous sight. Tsuna, on the other hand, had a bright smile, showing his dental arch with conviction. Every single people gathered inside that ball room were looking at the brunet, with admiration shining in their eyes — some with a sexual intention, however, those were quickly shoved with Reborn’s assassin aura.

            “Now make a wish, Juudaime!” Gokudera Hayato said with a grin, applauding excited. Tsuna sighed, with a gentle smile in his lips. Reborn rolled his eyes, only to listen to Hayato’s ‘Don’t make fun of Juudaime!’

            Tsuna tugged gently with his strong fingers the black suit that Reborn was wearing. The dark-haired teen peered at the brunet, confused. “You should make your wish too, Reborn.” At that the hitman laughed. He could hear some people saying how disrespectful the young teen was towards the tenth boss. He ignored, obviously. “Go on. Make your wish.” The Decimo said with a kind smile.

            Reborn remembered that the brunet thought that he never had a birthday party in his life. Well, that was, indeed, true. However, the dark-haired teen knew how a birthday party worked. And, even if he knew and hated his fatidic day with all his heart, he, somehow, felt happiness. Observing the brunet with a such kind expression, wanting to give the hitman the best first birthday party, he couldn’t deny that he loved it. A strange feeling at the base of his stomach again. Reborn twitched.

            The assassin snorted, closing his eyes and blowing the candles on the top of his cake — sixteen candles, even thought he lived for almost forty years. There was no wish, of course. That was too dumb and childish. The fire was distinguished and now he could only see the burned candle on the top of his cake. Tsuna chuckled. Reborn snapped his head only to look at the brunet with a murderous gaze. However, peering the young man, the hitman found that that was the most beautiful sight he’d ever seen.

            The young man had a satisfied expression on his face, with a proud grin growing on his reddish-like lips. Those hazel-colored eyes looked back at Reborn’s onyx-colored ones. “Happy Birthday, Reborn.” Tsuna said, hugging the dark-haired teen slowly. The hitman felt his face burn with embarrassment — and something else. And, suddenly, he felt the urge to tell the brunet something.

            “You look so pretty looking at me like that. I love it.” Reborn said with confidence and bravery. Tsuna jolted back, crimson red flush spreading through his cheeks; wide hazel-eyes observing the young teen. After a few seconds glancing the brunet, the hitman finally realized what he said. “I… I- I’m joking! As if you’re pretty!” Reborn said, feeling his cheeks burning. “Actually, I have no words to describe how you make me feel with that look of yours.” The hitman closed his mouth shut with both of his hands.

            Tsuna coughed, flattered and confused. Everyone in the party stopped only to watch this awkward scene between the world’s number one hitman and the Vongola Decimo. Reborn pulled his fedora, hiding his embarrassed. Quickly, the dark-haired teen ran, rushing toward his own room inside the Vongola Headquarters.

_What was that?!_

            The hitman kept thinking, feeling his heart race inside his chest. He’d never felt this way before. His stomach ache in a weird way, tingling at the base of his abdomen. His face was burning with embarrassment and something else. _Something else?_ ‘What is this feeling?!’

            ‘Is this… a disease?’ The assassin shocked his head. That was definitely not it. The young teen peered down, watching his abdomen, then peering up to the mirror, only to find his cheeks with a strong crimson red flush — not only on his cheeks, but on his ears and neck. He didn’t know what to do.

            And then, the young teen heard a knock on his door.

            “I’m coming.” He tried to sound normal, failing pathetically. The hitman opened the door, without hesitation, only to find the brunet with his hands in his pants’ pockets. “Tsuna…” Reborn tried to smirk, to show to his ex-student that that was only a joke; that that was only a plan of his to test his skills on hiding his emotions. However, his body refused to lie; refused to lie to Tsuna and himself. “What do you want?”

            “I need to ask you something, Reborn.” The hitman felt shivers travelling through his spine. Tsuna had a serious and deep tone, something that the hitman had only seen one time — when the brunet was pissed at his father. Reborn moved aside, letting the young man enter. The Decimo had his hazel-colored eyes, with a sharp look, glancing toward the teen. The dark-haired teen moved his head, running away from the brunet’s gaze. “Reborn, look at me.”

            ‘When did he got this dominant tone?!’ Reborn asked himself.

            “I love that tone of yours… Would you please start talking like these more often?” The hitman murmured, feeling something inside his stomach. Tsuna flinched, however, kept his serious gaze.

            “This is going to far, Reborn! Tell me, is this a joke? Are you doing this only to tease me?” Tsuna said, approaching the young teen. Reborn felt his heart racing. ‘What the hell?’ The hitman was desperate. Inside his mind he denied about his reactions towards the young man, however his body was burning with lust and desire. He craved the young man. Reborn looked away, stepping back. He would not accept this.

            But then, when he opened his mouth to tell that this was all a joke, something else came up. “I’m not joking… I want you so bad! Can’t you see?” Reborn widened his eyes, feeling his skin burn. ‘What am I saying?!’ The hitman said to himself, confused.

            “Reborn…” Tsuna murmured, with a confused expression. The brunet was deciding between whether he’d believe it or not. And, for a second, Reborn got a glimpse of Tsuna’s orange-colored eyes, shining quickly with desire. That sent shivers down his spine. “I’m going to ask you one more time. Are you joking?” The Decimo asked, serious. Reborn groaned, feeling something inside his body, that wouldn’t let him lie.

            “I’m not, Tsuna… please.” Reborn said with a lustful gaze. ‘Oh shit, that’s definitely not like me! Tsuna don’t listen to me!’ He said to himself. Even if he tried to warn the brunet that something was wrong with his body, he knew that he wouldn’t be able to tell him the truth. Suddenly, strong grips held his tights, pulling him up. Reborn felt his back hit the white wall behind him. “Ah…” He let a painful moan come out of his mouth. His dark eyes peered up, only to find those kind hazel-colored eyes, looking back.

            Reborn wanted to say something, however he felt soft lips crushing against his. Surprised, the young teen gasped, feeling the brunet’s tongue licking his lower lips, asking for permission. ‘What?’ He asked himself. His mouth opened without his consent — his body betraying him. And suddenly, inside his mouth, there was the brunet’s tongue mapping everything quickly with desire. It looked like the man needed that and was waiting for this for so long. Reborn moaned, feeling his body giving up at the man’s dominance. The brunet’s hands grasped the cheeks of the teen’s butt, pulling him close to his crotch. Tsuna moaned, feeling the young teen’s crotch rubbing against his.

            The tenth boss broke apart, leaving that delicious lips behind, only to catch the young teen’s chin. Biting softly, while leaving some saliva behind, the brunet went down, reaching for the teen’s neck. Reborn gasped, feeling his body warm. ‘Damn my body! I can’t control it!’ However, even if his mind was telling him to stop, his hands reached out for the brunet’s brown soft locks, pulling the man against his collarbone. Tsuna took that as an invite, grabbing the young teen’s button up shirt with one of his free hands. Quickly the dark-haired teen has been stripped, with his pants remaining. The free hand went up to one of the teen’s nipple, while his tongue sucked gently, but deliciously, the other nipple. Reborn moaned, already under the young man’s control.

            ‘How he’d learned this?! That’s way too good…’

            “Reborn… stop thinking too much about it.” Tsuna low voice sent shivers down the teen’s spine. The hitman peered down, only to find a smirk in the young man’s lips. Reborn wanted to roll his eyes, however, the brunet was fast, reaching his crotch. Instead he moaned at the sudden grasp. The tenth boss squeezed and gently spun his thumb at the head, letting the pre-cum run down his left hand. Feeling the slow, painful but delicious pump, Reborn lost his mind. “I always wanted this… really. Look at you. So beautiful.” Tsuna said, looking at the teen with a soft and kind gaze. “I wanted you to fuck me, but you just look so submissive right now.”

            Reborn groaned, his mind telling him to be angry at the brunet. However, he couldn’t think anymore. His body instinctually thrusted his hips against Tsuna’s left hand. The man smirked, feeling the young teen’s needs; hearing it and seeing it. Reborn was just so gorgeous as he moaned with desire. Tsuna saw the teen’s lips parting away, and that was his cue. Just like a lion hunting his prey, the brunet went forward towards the young teen’s lips, shoving his tongue inside, only to feel his mouth; only to feel the vibrations coming out of his mouth. Reborn felt the warm tongue against his, only to respond with a moan. Tsuna loved it.

            He heard the belt moving, and the flaps opening. The zipper going down.

            The teen opened his eyes, peering down in surprise. Tsuna’s hands grasping both his and the teen’s crotch. They both gasped, feeling the warm touch and delicious grip. Reborn continued to kiss the man, with his eyes half open, glancing those hazel-colored eyes filled with desire. Tsuna reached for the teen’s nipples again, leaving his lips behind. Reborn moaned hard, feeling both his crotch and nipples being fulfilled with those warm touches. “T-Tsuna… please!” The young teen stuttered, feeling his crotch tingling. He was almost done.

            “It’s ok, Reborn, I’m going to take care of you.” The brunet said, fastening the movements on the teen’s crotch. After a few seconds, Reborn jolted away, feeling his penis twitching. Tsuna peered down, to watch with passion the teen’s coming in his hands. The left hand went away, only to reach the young man’s mouth. Tsuna licked the cum, peering up to watch the teen’s reaction. Reborn flinched, finding that action hot and seductive. ‘God, this boy learned so much!’ He thought to himself, remembering those times where Tsuna was terrible at talking to girls. And now, there he was, driving Reborn to craziness. “It’s my turn now.”

            Reborn felt the grip in his butt cheeks hardening, pulling the young teen out of the wall, only to throw him to the soft bed. The hitman felt his back hitting the mattress hard. He peered up to find a pair of orange-colored eyes gazing him with lust and desire. ‘Is that… Dying Will Flame?’ The brunet reached out for the lube, spreading it on his own fingers. Reborn widened his eyes. “Tsuna!” The brunet smiled softly, knowing what the teen meant.

            “Relax, Reborn. This is your first time, right?” Tsuna asked, even though he knew what the answer was. Reborn growled, his mind slowly gaining the control of his body. The hitman had said that to people all the time. He remembered some women or men looking scared of having a big mass shoved inside them. He remembered assuring them that the pleasure would come right after the pain. However, he’d never expect that happening to him. “You know how this work. I don’t need to tell you that you’ll feel much better after the pain.” Tsuna approached the teen, playing teasingly with the teen’s butthole. Reborn flinched.

            “Hm!” The dark-haired teen groaned when he felt one finger inside him. Tsuna could feel Reborn’s walls tensing up, trying to push him away. However, the brunet knew better, grabbing the teen’s crotch precisely, bumping it slowly. Reborn suppressed a moan. “T-Tsuna!” The brunet felt the teen relax a bit, letting the man play easily with his anus. He introduced a second finger inside, hearing the teen’s soft moan.

            “I’m not even starting.” Tsuna said smirking. Those two fingers searched for the right spot, while his right hand bumped the member slowly. Reborn shivered, feeling his back arching upwards. Tsuna smiled. “Found it.” A third finger was introduced, and the teen didn’t even feel it. The brunet hit the prostate of the teen hard, wanting to hear those moans even more. Tsuna increased the speed in his left hand. Reborn moaned constantly feeling those fingers hitting that special spot. Then, suddenly, he felt empty. Tsuna was now putting a condom in his crotch.

            “Tsuna… wait!” Reborn tried to say him to stop, however, his body was still desiring the young man. And then he felt the crotch of his ex-student, slowly entering. He was filled with the young man. Tsuna took a deep breath, holding the teen’s body tenderly, digging his face on the teen’s neck curve. Reborn felt the warm breath on his neck and his butt being filled with the brunet’s crotch. “Hm… Tsuna, you can move.” Reborn said, even if he didn’t want to. However, now was too late.

            Tsuna held the teen’s hips strongly, thrusting hard. Reborn gasped, feeling the crotch hitting his prostate instantly. ‘On the first try… this guy!’ The hitman said to himself, feeling the young man moving one more time, hitting the prostate again. “You know… I wanted to show to you that I’m worthy, that I know how to fuck or be fucked!” The brunet said, thrusting hard again, reaching out for Reborn’s hands. The teen peered up, watching those shiny orange-colored eyes. “I studied a lot with both men and women. And!” He thrusted, looking directly into those onyx-colored eyes. “That’s the result!” Tsuna hit the prostate again. “That’s my resolution.”

            Reborn was hypnotized by those orange-colored eyes, and the pleasure consuming him. Tsuna reached down, crushing their lips together again. The hitman now had the power to push the man away, however, he couldn’t. _He didn’t want to_. Their tongues fought searching for pleasure. Tsuna’s tongue moving with passion, while Reborn’s moved with doubt. He wandered if doing that with his ex-student was correct.

            “Don’t doubt.” Tsuna said, thrusting one more time. Reborn moaned, looking into those lustful, but lovingly, eyes. “I’m here because I want to. Don’t doubt that. I’m here because I love you since I was fifteen.” The young man confessed, grabbing the young teen’s neck, pulling him close. Their lips were together one more time. And Reborn couldn’t deny it. He loved it. He loved it all.

            “Tsuna…” The hitman moaned softly, glancing the man in front of him. His hand pushed the brunet, forcing him to sit. Reborn sat on him, riding slowly in Tsuna’s crotch. They both moaned. The brunet grasping strongly those hips again, helping the teen to ride. They both looked needy; they both wanted it. Reborn grabbed the brunet’s face, pulling him closer again. Tsuna tilted his head, only to deepen the kiss. Reborn moaned.

            The brunet thrusted the young teen hard, hitting the prostate one last time before coming inside the young teen. Reborn felt the cum running down through his anus, dirtying their skin. Tsuna pulled out, watching the teen almost fall onto the mattress. Both looking exhausted. The brunet approached again, kissing fondly the teen’s lips, and right after his forehead.

            “I love you.”

            “…” Reborn watched those typical hazel-colored eyes, with a kind and lovingly gaze. The teen sighed. “I… love you too.”

            ‘Damn… I can’t control it.”

            Tsuna hugged the young teen. Both falling onto the bed to sleep.

**Author's Note:**

> Maybe one day I'll write a 'payback' with seme!Reborn. But for now, we only have this.


End file.
